Common milkweed provides nectar for butterflies, and is the only food source for monarch caterpillars, but is too aggressive for your garden?
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Should You Grow Common Milkweed?
With the declining population of monarchs in the news so often these days, many home gardeners are choosing to add milkweed to their gardens to help support this beautiful butterfly. This is a fantastic idea. I encourage everyone to plant as much milkweed as they possibly can.
But there are many species of milkweed. It’s best to choose species that are both native to your area as well as appropriate for your garden space. Common milkweed (Asclepias syriaca) has a wide native range and is easy to find, but it also has some aggressive properties that may not make it right for your butterfly garden.
What Does Common Milkweed Look Like?
Common milkweed can be found throughout most of the Eastern U.S. and Canada (with the exception of Florida), west to the Rocky Mountains. It grows in a variety of soil conditions, usually in full sun, and is often found in ditches and roadside medians. It can grow quickly to 5 feet tall, with broad leaves and a stout stem, topped by clusters of pink flowers that butterflies visit for nectar.
In the late summer, the flowers give way to large seed pods. They burst open to send their feathery-topped seeds into the wind to spread for the following growing season.
Learn if you should be removing milkweed bugs from your plants.
Common Milkweed Benefits for Monarchs
The leaves are used by monarch caterpillars for food (milkweeds are their only food source) and are vital to the species’ survival.
Common Milkweed Can Spread Aggressively
Anyone in its native range (zones 3 to 8) with space for a wildflower garden can consider common milkweed. But gardeners should be aware that this species is considered very aggressive. It spreads not only by seed but by underground rhizome, and can be very difficult to control. Once established, it’s nearly impossible to get rid of.
If you have a large area available, or aren’t worried about the possibly “weedy” appearance of this plant, you should find a local source for some seeds and add it to your property.
Milkweed Rash and Allergies
If you have a small yard, are outside its native range, or have a latex allergy, you should think twice. Common milkweed, like other milkweed species, contains latex. This causes the foliage to be very sticky and can lead to rashes in those allergic to latex.
Is milkweed poisonous to people and pets?
How to Control the Spread of Common Milkweed
“How do I keep common milkweed from spreading in my garden? Or is it better to plant a different variety?” asks Birds & Blooms reader Judy Roberts of Graytown, Ohio.
Horticultural expert Melinda Myers says, “We appreciate milkweed’s many benefits for monarchs and other pollinators, but the aggressive nature of common milkweed (Asclepias syriaca) allows it to quickly overtake a garden or small landscape. To prevent reseeding, you can remove the seed pods before they open, but common milkweed readily spreads by rhizomes 9 inches or more below ground, making it difficult to contain.
All types of milkweed support monarch caterpillars, and females lay their eggs on various milkweed species. Common and swamp or red milkweed (Asclepias incarnata) are favorites, but research found that the monarchs’ egg-laying preferences can change depending on the time of the season, the maturity and robustness of the plant, and the prevalence and habitat of the species they encounter.
Swamp milkweed is much less aggressive than common milkweed, tends to form a clump and grows 2 to 5 feet tall. Butterfly millkweed (Asclepias tuberosa) is also suitable for home gardens with well-draining soil and full sun. Both varieties are native throughout much of the United States and Canada and are available to purchase as plants and seeds.”
Backyard tip: You can try growing common in sunken pots in the ground to limit the rhizome spread.
About the Expert
Melinda Myers is the official gardening expert for Birds & Blooms. She is a TV/radio host, author and columnist who has written more than 20 gardening books. Melinda earned a master’s degree in horticulture from the University of Wisconsin-Madison.
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